用于重载和精确定位线性尺蠖电机上的巨型磁致伸缩夹紧机构【中文7120字】
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用于重载和精确定位线性尺蠖电机上的巨型磁致伸缩夹紧机构【中文7120字】,用于,重载,以及,精确,定位,线性,尺蠖,电机,机电,巨型,伸缩,夹紧,机构,中文
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Mechatronics 21 (2011) 92 99Giant magnetostrictive clamping mechanism for heavy-load and precise positioning linear inchworm motorsBintang Yang a, Guang Meng a, Zhi-Qiang Feng b, Dehua Yang ca State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai, Chinab Laboratoire de Mcanique et dnergtique dvry, Universit dvry-Val dEssonne, vry, Francec Institute of Astronomical Optics and Technology, Chinese Academy of Science, Nanjing, Chinaa r t i c l e i n f o Article history:Received 17 November 2009Accepted 27 August 2010Available online 25 September 2010Keywords:Giant magnetostrictive material Blocked-forceInchworm clamping principle Precision linear motora b s t r a c t This paper focuses on the development of a novel clamping principle and the mechanism that may beused to realize a linear motor capable of performing not only large thrust but also secure movement with high blocked clamping force. To verify this principle, a clamping prototype (size: /32 130 mm) is con-structed and tested. It generates a clamping force of 1050 N with an initial experimental set-up, and, a clamping force up to 1525 N with a modied set-up employing a hydro-press bench clamp. The theoret- ical and numerical analyses are carried out and suggest that the mechanism may generate a clamping force up to 2148 N with an adequate rigid guide-way.。 2010 Elsevier Ltd. All rights reserved.1. IntroductionUsing smart-material actuators rather than linear motors has been the focus of many works, such as the work in precise posi- tioning over micron-level span, in active vibration control, etc. Delivering and accumulating the high precision deformation of solid-state smart-materials is a critical research task to challenge the usual belief that the deformation of smart-materials is too small to adapt in long stroke driving applications. The feasibility of applying inchworm moving principle to build a linear motor by step accumulation has attracted those who aim to change the small span driving actuator into a precise long distance driving motor. Different prototypes of linear motors have been developed in the last decade, mainly based on the integration of smart-mate- rials and inchworm driving principles such as the piezoelectric driving 1,2 , the giant magnetostrictive driving 3,4 and piezo- magnetostrictive hybrid driving 5,6 . Although researchers have recognized the importance of the clamping mechanism in inch- worm motors, they have emphasized more on its linear driving part and on the solution to the inherent problems such as hyster- esis 7 and Joule heat 8 . In fact, we believe that without an ade- quate clamping mechanism, it is difcult to achieve a high precision smart-material inchworm motor even the above-men- tioned problems could be well solved. For instance, in the previous work 9 , due to the fact that the eletromagnetic clamping mecha- nism brings about sway and tilt at doing clamping actions, the Corresponding author. Tel.: +86 21 34206332x836.E-mail address: btyang (B. Yang).small inchworm motor can hardly perform the nominal nanomet- ric step traveling even its linear driving part is able to render nano- meters elongation. So the clamping mechanism can affect the motor both on the positioning precision and on the thrust capacity. The giant magnetostrictive material is largely used in developing inchworm motors because it possesses interesting properties of high compression strength, high output force and giant magneto- striction. In addition, it has the potential to generate high blocked clamping force in static case. However, it is difcult to fulll blocked-forcing in movement regime. In this work, we propose a novel blocked-force clamping principle and the corresponding mechanism using the giant magnetostrictive material TeDyFe. An experimental set-up and a numerical model are developed to val- idate the proposed principle.2. Magnetostrictive clamping mechanism of linear inchworm motorA typical structure of a linear inchworm motor can be illustrated as an H-shape structure, as shown in Fig. 1. The motor is most necessarily constructed by Parts A and C (the clamping mechanism), Part B (the driving mechanism) and Part D (the guide-way). The motor can move when Parts AC are excited in se- quence and alternately to do the action of clamping-on/off by A and C against D, and stretching-on/off by B (see 9 for more de- tails). The parts A and C are placed into the guide-way D to gener- ate a deformation in the vertical direction, while the driving part B is congured to produce an elongation in the horizontal direction.0957-4158/$ - see front matter 。 2010 Elsevier Ltd. All rights reserved. doi: 10.1016/j.mechatronics.2010.08.011Contents lists available at ScienceDirectMechatronicsjournal homepage: www. /locate/mechatronics B. Yang et al. / Mechatronics 21 (2011) 92 99 93Fig. 1. Schematic of a typical inchworm linear motor.The rigid guide-way D is used to guide the linear moving and to provide clamping friction as it squeezes the top and bottom ends of A or C. In this work, we have chosen the TeDyFe giant magneto- strictive material (GMM) to make the clamping mechanism. According to 7,10 , GMM has almost all the properties required for a clamping application, as listed in Table 1. Some competent clamping technologies using smart-materials have been developed and reported in the literatures 11 13 . Kim and Doo 11 pre- sented a self-moving cell mechanism that can execute both driving and clamping actions during an inchworm movement. The cell is basically a ring mounting a GMM rod and a solenoid inside. When the GMM rod is not excited, the ring is deformed by the pre-stress against the walls of a guide-way. The elasticity of the ring gener- ates the needed clamping-on force. When the GMM rod is excited, the ring stretches along with the rod elongation and shrinks in the direction perpendicular to the rod axis so as to realize clamping-off action. Park et al. 12 and Erismis et al. 13 reported another clamping method in which a micro-ridge MEMS technology is used to generate large clamping force. According to their works, the Cell-clamping mechanism can produce a large clamping force by the ringelastic deformation against the guide-way which makes the cell move linearly without slippage. The micro-ridge-clamping mecha- nism can also produce a large clamping force due to the enhanced friction by the micro-ridges or saw tooth. We realize that there is still room for improvement through analysis of the potential limi- tations of the above two clamping mechanism types. In the case of cell-clamping mechanism type, the maximum clamping force is most likely dependent of the elasticity of the ring and the pre- stress conguration of the GMM rod. The acquisition of sufcient stretching of the cell to release the clamping force requires rela- tively large magnetostriction, which may affect the GMM rods elongating resolution, and in turn the positioning precision. In the case of the micro-ridge-clamping mechanism type, the step- moving resolution could be conned by the size of the micro-ridge. The larger the micro-ridge is, the less the resolution becomes. Stable nanometric positioning appears to be difcult if the ridge size is over nanometric range.Aiming to improve the current smart-material clamping tech- nology, a novel giant magnetostrictive clamping mechanism is pro- posed and described in the next section. This clamping mechanism can render a large and adjustable clamping force as a result of fully demonstrating the GMM property in high stress. It can also realize a pre-clamping regime enabling a no-power clamping behavior that is necessarily important for fastening the mechanism body when it works at certain slantwise positions and on the power- off occasion.3. Principle of the giant magnetostrictive clamping mechanismThe magnetostriction phenomena can be described as the deformation of body with respect to a change of its magnetiza- tion characterized by an even function of the magnetic eld, which implies that magnetostriction is proportional to strength H of the external activated magnetic elds, and the strain of magnetostrictive rod is independent of the sign of the applied longitudinal magnetization. Another fundamental effect to real- ize the new magneto-elastic clamping principle is that a GMM rod can perform both expansion and contraction by magnetizing it in sequence with two magnetic elds, H1 and H2 as illustrated in Fig. 2, both having a magnetic eld but with different strength and in opposite directions. This is basically how elongation and contraction are achieved with a GMM rod. Precisely owing to this effect, the clamping-on or clamping-off actions are realized. Therefore, the principle of the new GMM clamping mechanism is established. Accordingly, a clamping mechanism has been real- ized as shown in Fig. 3. The clamping mechanism is designed considering electromagnetic and mechanical aspects to achieve an efcient magnetization to drive the GMM rod. The clamping mechanism consists of an active GMM rod preloaded symmetri- cally in a rigid permanent magnet barrel housing and sur- rounded by a solenoid. The preload is applied by two Belleville washers inserted on both sides between the housing covers and the rod. Details on the electromagnetic conversion (solenoid and magnetic circuit) and on the pre-stress mechanism are given in 9,14,15 . The clamping regime is thus pre-biased by the per- manent magnet barrel for H1 and is excited by the solenoid forH2. Through controlling the exciting eld H2, an entire clampingprocess can be performed as illustrated in Fig. 4. M and G indi- cate respectively the clamping mechanism and the rigid guide- way. To mimick the actions of M of the motor walking from left to right side in the guide-way G, six procedures are necessary and described as follows:Table 1Corresponding properties of GMM in clamping application potentials. Properties of GMM Parameters Clamping applicationGiant and solid-state magnetostrictionCompressive strengthInstant response time1500 2400 (ppm) Large and high precisiondeformation for clamping action700 (MPa) High pressure1 ls Wideband frequency, no clamping delayEfcient energy transductionCoupling factor: 0.7 0.75; Energydensity: 14 25 (kJ/m 3); Conversionefciency: 49 56 (%)Efcient energy transduction from electromagnetic to mechanical, easy clamping control, adjustable clamping forceAvailable pre- biased magnetostriction500 1000 (ppm) Both extension and contractionclamping action available by DC or permanent-magnet biasingFig. 2. Illustration to the magnetostrictive expansion and contraction.94 B. Yang et al. / Mechatronics 21 (2011) 92 994. Experimental verication to the clamping principleFig. 3. Structure of the clamping mechanism and the prototype photo.Fig. 4. Illustration to the principle of the magneto-elastic clamping mechanism.(1) M is permanent-biased by the magnet barrels for an initial stretch.(2) M is contracted by an exciting eld opposite to the perma- nent one and then put into G.(3) M comes into a pre-clamping or clamping-on state by cut- ting off the exciting eld. In this case, M tends to recover its initial state and thereby to be squeezed in the rigid guide-way (the guide-way width is smaller than the length of the clamping mechanism in initial state).(4) The clamping force by far can be adjusted by changing the exciting elds.(5) M returns to its pre-clamping state when cutting off theexciting eld.(6) M is contracted by applying a eld opposite to the perma- nent eld and get out of G and then recovers its initial state.By far, an entire clamping process has been performed. This also illustrates the application of a novel clamping principle to the accomplishment of blocked-force clamping in movement.Fig. 5 shows the experimental set-up and results for testing the expansion and the contraction capacity of the prototype with a sizeof / 32 130 mm, driven by a / 10 100 mm TbDyFe rod(purchased from Jiaog. Rare earth material Co., Ltd.). The prototype is excited with a solenoid (670 turns, 100 mm of length, 1 mm of wire diameter, 10 mm of inner diameter, 30 mm of outer diameter and Gcoil = 0.1098) and pre-biased by two permanent magnet bar- rels (NdFeB, 2 mm of wall thickness, 50 mm of length, 32 mm of outer diameter). Experimental tests show that the permanent mag- net barrels are capable of providing a magnetic intensity around15 kA/m corresponding to the half saturated magnetostriction.Meanwhile, 78 MPa pre-stress is settled by means of two Belle- ville washers (stiffness: 3.0037 10 6 N/m) as in a previous study9 . The washers are inserted between the covers (Ni Fe alloy, 3 mm of thickness, permeability: 10,000 l0) and the rod. A Key-ence LK-G30 laser sensor is used to measure the net displacement. Fig. 5 displays the prototype deformation versus the scanningmagnetic elds from - 53.6 to 53.6 kA/m (corresponding to a ACcurrent varying from - 8 to 8 A). According to the result, the max- imum contraction - 53 lm under - 13.4 kA/m (- 2 A current) elec-tromagnetic elds and the maximum stretch 48 lm under 53.6 kA/ m (8 A current) elds, so that the total 101 lm variable displace- ment was reached. This displacement capacity of the clamping mechanism is supposed enough to meet the requirement of the proposed clamping principle. And we have further completed an- other experiment in order to verify each clamping action of the new clamping principle that is illustrated in Fig. 4. The experimen- tal set-up is shown in Fig. 6. A leading-screw pressing jig and a pressure sensor are employed. The sensor is sandwiched between the lower side of the leading-screw and a rigid aluminum bar which is against the upper side of the standing clamping mecha- nism on an aluminum base. The aluminum bar is used not only for its capability of protecting the magnetic elds from leakage but also for its facility to measure the displacement by reecting the sensors laser spot.In order to simulate the clamping process and to demonstrate the related clamping functions, two series magnetic elds (i.e. two series currents) have been applied to the prototype. Both the clamping force and the clamping displacement have been moni- tored and measured through the displacing sensor and the pres- sure sensor. It should be noted that although the constructed guide-way can be convenient to measure the clamping change in displacement, it is still hard to be completely rigid for measuring the real clamping force as the strain-gauge pressure sensor itself will deliver a withdrawing displacement. Nevertheless, we haveFig. 5. Displacement generated by the prototype by applying scanning magnetic elds (scanning currents vary from - 8 A to 8 A) and experimental set-up.B. Yang et al. / Mechatronics 21 (2011) 92 99 95Fig. 6. Experimental set-up and the equivalent mechanical model.Fig. 7. Generated displacement and clamping force under different constrains by series square currents exciting.made the guide-way to be as rigid as possible by applying con- straining force up to 700 N through the leading-screw press jig. The experimental results are presented in Figs. 7 and 8, wherein the evolution of clamping displacements is related to the six proce- dures of an entire clamping process as shown in Fig. 4. In Fig. 7, the exciting elds are generated by a series of square currents only, while in Fig. 8 the magnetic elds are generated by another series of currents that comprise square currents and a half-sine current. Moreover, during the test, different forces for constraining the guide-way are applied with a magnitude of 100 N, 300 N, and 700 N, respectively.From the results we observe that the new clamping mechanism can be easil
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